Explosive Forming Research Articles

Near-Contact Explosive Forming

The method of near-contact explosive forming with controlled media is defined and described. Economical examples of the shaping of flat or curved plates with four flat edges, expansion of tubes into tubesheets or outer tubes, and expansion of plugs into tubes are given.

Stress distribution and flexibility of the suction bend of the primary sodium pump—LMFBR-SNR 300

Hydrodynamic aspects lead to the design of a special smooth suction bend for the LMFBR-SNR 300 primary sodium pump. This bend is built up from two symmetrical halves, formed from plates by explosive forming. For the nuclear piping system design, the ASME Boiler and Pressure Vessel Code —Section III 1 gives formulae for the simplified stress analyses by using the stress indices and flexibility factors. The application of these formulae to the prediction of the stresses and flexibility of the suction bend considered does not guarantee the reliability of the results. To achieve a more accurate prediction of the bend's stresses and flexibility linear stress analyses are carried out based on two different methods. In the first method the bend is schematised by various toroidal segments with bend parameter λ ranging from 0·049 to 0·22. Each segment is analysed as described below. Internal pressure: Stress analyses are carried out using the KSHEL computer program developed by Kalnins and based on his theory. 2 In- and out-of-plane bending: Based on the energy equations of von Karman 3 and Vigness, 4 a theoretical solution was developed by Rodabaugh and George. 9 Applying the principle of least work gives the following equation: [D(λ,r,p,n,E)]{c n} = {−3,0,0,0,…} T where D is a symmetrical band matrix and c n is the modified unknown coefficient of the trigonometric series of the displacement field. The stresses and flexibility could be determined by substituting c n in the appropriate equations. The membrane circumferential stress distribution obtained by Rodabaugh and George was modified by Dodge and Moore 6 based on Gross's solution. 8 The computer program PIPEBEND, based on the above-mentioned solutions, is developed for calculating the stresses and flexibility of each toroidal segment. The second method deals with three-dimensional stress analysis. This is necessary in order to investigate the influence of change of curvatures and cross-sections (neglected in the first method). Modelling is carried out for the symmetry of half of the complete suction bend, applying the thick shell element QUABC9 of the ASKA system. Application of this element for thin shell problems requires the reduction of the number of integration points. For the considered model, a 2 × 2 reduced integration scheme is chosen for the transverse shear component only. The results of both methods were compared and it was concluded that, for internal pressure and pure—or nearly pure—bending load, adequate prediction of the stresses and flexibility can be obtained by the first method.

Increasing the strength properties of sheet parts by explosive forming of them with optimization of the production parameters

Increasing the strength properties of sheet parts by explosive forming of them with optimization of the production parameters

Numerical solution of transient nonlinear problems

Abstract The paper is concerned with computational aspects of nonlinear and transient finite element analysis. Particular emphasis is placed on the inelastic response behaviour of structures and continua, respectively, when exposed to quasistatic and dynamic environments. Several examples illustrate the application to different engineering disciplines such as thermal shock behaviour, explosive metal forming and wave propagation. The objective is twofold, (i) to demonstrate dominant features of explicit and implicit time-marching algorithms (linear and cubic Hermitean expansions with different weighting strategies) and (ii) to show the solution of relevant engineering problems. The paper is divided into three parts addressed to 1. 1. Computational strategies for nonlinear and transient analysis, 2. 2. Inelastic analysis of quasistatic motions, 3. 3. Dynamic analysis of inertial and wave propagation problems.

Numerical simulation on a computer of the process of explosive forming

Numerical simulation on a computer of the process of explosive forming

Annealing of iron deformed by rolling and explosive forming

1. Lowering the original temperature of iron samples to −196° leads to a continuous increase of the hardness with increasing pressures of explosive forming up to 600 kbar. With identical values of true strain the samples deformed by explosive forming have a higher hardness, larger width of x-ray lines, and higher electrical resistivity than samples deformed by rolling. 2. Regardless of the method or extent of deformation, four stages of the recovery of properties are observed in deformed iron during annealing: I) 0–130°; II) 130–260°; III) 260–410°; IV) above 410°. 3. The first stage is due to the movement of carbon from the solid solution to dislocations and partial entrapment of carbon by vacancies. The second stage is due to dissociation of carbon—vacancy complexes and migration of the components and also to the beginning of carbide precipitation.

Hardening of quenched low-carbon steel during explosive forming

Hardening of quenched low-carbon steel during explosive forming

Traumatic tattooing.

Traumatic tattoos may be classified into abrasive and explosive types. The abrasive form leaves the pigment deposit in the more superficial layers of the skin. Explosive forms of traumatic tattooing usually have a central focus of deeply embedded detritus with more superficially placed particles radiating from the central focus. In either form, the best results are achieved by immediate meticulous care of the wound. Many instruments and abrasive devices have been used to remove the embedded pigmented debris, yet the stimplest and most successful is the sterile, hard, natural-bristle toothbrush. This can easily be sterilized, packaged, and kept available in the emergency room and in the operating room.

Principles underlying the uniform breakdown of rocks by an explosion

The problem of obtaining fragments of specified dimensions by means of an explosion is extremely important in the present-day mining industry. It is well known [1] that under ordinary conditions explosions yield fragments of widely varying shapes and sizes. It is economically undesirable to produce either very large peices which are inconvenient for processing or unduly fine ores and rocks. The various explosive devices [2–4] used at the present time in mines and quarries fail to provide an adequate solution to this problem. This paper sets out a fundamental form of explosion, theoretically producing absolute uniformity of fragment size.

Acoustically induced explosions of superheated droplets

A novel technique for measuring the tensile strength of liquids was recently reported [R. E. Apfel, J. Acoust. Soc. Am. 49, 145 (1971); Nature (Phys. Sci.) 233, 119 (11 Oct. 1971)]. In this technique, a droplet of the sample rises slowly in a column of another liquid, the ’’host,’’ in which it is nearly insoluble. When the droplet reaches a certain position in the host, an acoustic standing-wave field at about 50 kHz is established in the column, serving two purposes: (1) to balance the buoyancy force on the droplet and thus levitate it and (2) to rend the sample apart by raising the acoustic pressure to a great enough amplitude. If the droplet is simultaneously superheated, the cavitation event takes the form of an irreversible explosion of the sample into its vapor. Taking advantage of the levitation scheme, we have filmed this explosion with both diffuse and shadow lighting at about 3500 frames/sec; this shows resonant oscillations and what appears to be jet formation during the collapse of the vapor bubble. Subject Classification: 35.68; 25.60.

Single or double vaccination schedules in sheep against experimental infection with Salmonella typhimurium or Salmonella bovismorbificans.

Abstract Extract Outbreaks of ovine salmonellosis in New Zealand are more common during the period January to May and losses arising from either the explosive form of outbreak or protracted flock infection often warrant the immediate use of vaccine. The significant protection afforded by inactivated bivalent vaccines has been demonstrated in both experimental and field trials (Beckett, 1967; Cooper, 1967; Wallace and Murch, 1967; Rudge et al., 1968; Davis, 1969).

Acoustic Cavitation: Film Sequences and Threshold Measurements

A novel technique for measuring the tensile strength of liquids was recently reported [R. E. Apfel, J. Acoust. Soc. Amer. 49, 145 (1971); Nature (Phys. Sci.) 233, 119 (11 Oct. 1971)]. In this technique a droplet of the sample rises slowly in a column of another liquid, the “host,” in which it is nearly insoluble. When the droplet reaches a certain position in the host, an acoustic standing-wave field at about 50 kHz is established in the column, serving two purposes: (1) to balance the buoyancy force on the droplet and thus levitate it and (2) to rend the sample apart by raising the acoustic pressure to a great enough amplitude. If the droplet is simultaneously superheated, the cavitation event takes the form of an irreversible explosion of the sample into its vapor. Taking advantage of the levitation scheme, this explosion has been filmed with both diffuse and shadow lighting at about 3500 frames/sec and shows resonant oscillations and what appears to be jet formation during the collapse of the vapor bubble. New results for the tensile strength of superheated n-pentane as a function of temperature have been measured and appear, like previous results for ether and n-hexane, to be in reasonable agreement with the theory of homogeneous nucleation. [Work supported by the U. S. Office of Naval Research, Acoustics Program.]

Finite Deflections of Circular Membranes

The behavior of membrane-like structures is of interest in conjunction with problems concerning slack diaphragms, inflatable structures, explosive forming of metals, interpretation of hydrostatic bulge tests, and continuous analysis of cable nets. For rotationally symmetric loadings of initially flat elastic circular membranes (the subject of this note), the Foppl-Von Karman equations are usually used to carry out the stress and deformation analysis. These equations are valid for moderate rotations and deformations and small strains. The membrane form of the equations given by Reissner represents a generalization of the Foppl-Von Karman theory to the case of arbitrarily large rotations and deformations, while retaining the small strain assumption. The purpose of the present work is to obtain some solutions to the Reissner membrane equations and compare these results to those previously found from the Foppl-Von Karman equations.

A comparison of the effects of explosive forming and static deformation on the mechanical properties of pressure vessel steels

The mechanical and impact properties of ASTM A285 Grade C and A515 Grade 70 steels were determined after either explosive forming or statically straining to the same level of effective strain. After explosive forming and a standard stress relief anneal, both steels met boiler code specifications. Statically prestraining reduced the impact strength of the A285 steel, whereas explosively formed A285 steel had impact properties comparable to as-received stock. The impact properties of A515 steel strained to about 4 pct effective strain were comparable regardless of method of strain introduction. At strain levels of 35 pct strain the cold-rolled A515 steel had greater impact resistance and lower DBT values than explosively formed steel.

A fragmentation problem for an elastic plate

We examine fragmentation in a linearly elastic plate subjected to the action of a moving load. The load is assumed to “run” at a “supersonic” constant velocity along one of the plate's sides. A loading of this type is encountered, for example, in explosive forming and explosive welding, during an oblique collision of two plates, etc. Fragmentation is understood as destruction of solid or liquid bodies occurring as a result of compression-wave reflection from free surfaces or from the interface between two bodies, one of which possesses a lower acoustic stiffness. Many interesting cases of fragmentation are described in Rinehart and Pearson's book [1], which also contains extensive literature references on the subject. Most of these papers give an acoustic interpretation of the fragmentation phenomenon with conditions of one-dimensional deformation. Lenskii [2] has tried to apply the theory of elasticity to the description of the fragmentation phenomenon in a plate experiencing a concentrated force. Ogurtsov [3] has obtained an exact solution to a stress problem for an elastic plate under a concentrated load; however, due to its complexity, his solution has yet to be applied to the fragmentation problem. In the present formulation of the problem, a simple exact expression for the stress waves in a plate, from which the fragmentation parameters can be determined, is obtained with relative ease. The solution can be used to obtain certain fragmentation data for a plate under a concentrated load, and also for an explosion in an elastic half-space. For example, it is possible to determine the approximate form of fragmentation cracks and formations near the epicenter.

Some Propositions on Electrical Discharge Forming

The E. D. F. has been recently developed to metal working which i s one of the high-energy-rate forming processes and this technique is industrially putting into practice.This paper deals with some propositions on E. D. F. in oposition to the usual E. D. F. with twin rod electrode.(1) An E. D. F. of single electrode type is characterized by that a work metal to be deformed is used as one of electrodes, resulted in simplification of a forming apparatus and a electrode composition.(2) An E. D. F. of multi-electrode type has successfully developed for the purpose of plastic deformation of large metalic plate in the same manner as explosive forming.(3) On the other hand, it is possible to deform a work metal by using water hammering of high-speed and high-pressure water jet which is spouted out from an orifice of the vessel, in which an impulsive high current discharge is generated.These methods proposed by the authors have many merits it comparison with the conventional E. D. F. process.

Explosive Forming of Hemispherical part used to Rocket

Explosive Forming of Hemispherical part used to Rocket

Thermal recovery in 304 stainless steel following explosive shock loading and explosive forming

The annealing behavior of type 304 stainless steel sheet samples shock-loaded at pressures between 750 and 1200 kbar, and cylindrical samples explosively expanded between 32 and 62 pct is characterized by rapid (catastrophic) hardness recovery between 750° and 850°C. Apparent aging effects, the occurrence of precipitates and dislocation loops of varying sizes, and a preferential etching at grain boundaries in thin electropolished foils is observed at 750 and 1200 kbar and 32 and 62 pct. Electron transmission microscope observations revealed that the catastrophic recovery and subsequent pseudorecrystallization were essentially synonymous, with no apparent nucleation and growth of new grains. Recovery is characterized mainly by the collapse of deformation twins and the accelerated annihilation of dislocations. Considerably less recovery is observed for lower shock pressures (<750 kbar), and for less explosive expansion (<25 pct) as evidenced by the presence of numerous dislocations at temperatures where complete recovery has occurred for higher pressure samples. It is suggested that a nonequilibrium vacancy concentration exists at the higher shock-pressures and larger degrees of explosive expansion, and that this feature is largely strain-rate dependent.

Comparison of Recovery and Recrystallization in Stainless Steel Following Plane-Wave Shock Loading and Explosive Forming

Comparison of recovery rates in materials deformed by a unidimensional and two dimensional strains at strain rates in excess of 104 sec.−1 was performed on AISI 304 Stainless Steel. A number of unidirectionally strained foil samples were deformed by shock waves at graduated pressure levels as described by Murr and Grace. The two dimensionally strained foil samples were obtained from radially expanded cylinders by a constant shock pressure pulse and graduated strain as described by Foitz, et al.

Stresses in cylindrical pressure vessels with end closures previously shaped by free explosive forming

The stress analysis of photoelastic models of pressure vessels with drumheads shaped by free explosive forming showed that discontinuities of profile of up to 34° at the drum-knuckle junction are permissible because the resulting peak knuckle stresses are lower than in vessels with equivalent torispherical drumhead. Free explosive forming, by forcing flat plates through ring dies, produces repeatable, approximately torispherical shapes. For annealed mild steel the geometric and explosion parameters have been related to permit prediction of dish shapes. It was found that no size effect existed.